code: def create_backend(
      self, project: ProjectModel, config: VastAIConfigInfoWithCreds
  ) -> BackendModel:
      if config.regions is None:
          config.regions = REGIONS
      return BackendModel(
          project_id=project.id,
          type=self.TYPE.value,
          config=VastAIStoredConfig(
              **VastAIConfigInfo.parse_obj(config).dict()
          ).json(),
          auth=VastAICreds.parse_obj(config.creds).json(),
      )
  
file_path: dstack/src/dstack/_internal/server/services/backends/configurators/vastai.py
imports: import json
  from typing import List
  from dstack._internal.core.backends.vastai import VastAIBackend, api_client
  from dstack._internal.core.backends.vastai.config import VastAIConfig
  from dstack._internal.core.models.backends.base import BackendType, ConfigElementValue, ConfigMultiElement
  from dstack._internal.core.models.backends.vastai import AnyVastAIConfigInfo, VastAIConfigInfo, VastAIConfigInfoWithCreds, VastAIConfigInfoWithCredsPartial, VastAIConfigValues, VastAICreds, VastAIStoredConfig
  from dstack._internal.server.models import BackendModel, ProjectModel
  from dstack._internal.server.services.backends.configurators.base import Configurator, raise_invalid_credentials_error
label_desc: Use image node_id 3 for calling the VastAIConfigurator obj's underlying member method code with example usage: obj.create_backend(project, config) and returns: BackendModel